1. Field of the Invention
The present invention relates to an auto document feeder, which is attached to, e.g., an electronic copying machine, and particularly has an improved original discharge process.
2. Description of the Related Art
As a conventional auto document feeder to be attached to an electronic copying machine, U.S. Pat. No. 4,849,786 is known. This feeder automatically separates a plurality of originals stacked on a paper supply tray, and feeds the separated originals to an image scanning position on an original table one by one. After an image-scanned original is discharged, this feeder feeds the next original to the image scanning position.
In the auto document feeder, an operation for discharging a scanned original onto a paper discharge tray is performed by a conveyor belt on the original table. The timing of this operation is synchronized with an original feeding operation for feeding an original to the image scanning position. More specifically, a process for discharging one image-scanned original present at the image scanning position onto the paper discharge tray, and then feeding the next original to the image scanning position is repeated, thus attaining original replace processing.
The conventional auto document feeder repeats a process for feeding an original to the image scanning position on the original table one by one, discharging the scanned original from the original table, and simultaneously feeding the next original to the image scanning position, regardless of the original size in the original feed direction. For this reason, as the original size in the original feed direction becomes shorter, the interval between adjacent originals is widened, and the time required for replacing originals is undesirably prolonged.
In the conventional auto document feeder, when two adjacent originals are to be successively discharged onto the paper discharge tray, a normal feed speed is switched to a low feed speed during a feed operation of each original. For this reason, when the discharge interval between originals to be discharged is shortened, before the first original is discharged from a paper discharge port and lands on the paper discharge tray, the next original is discharged from the paper discharge port, and the leading end of the latter original collides against the trailing end of the former original. Thus, the original discharged first may jump out forward, or the original discharged later may be jammed at the paper discharge port.